This invention relates to improvements in speed control mechanisms for free-running conveyors of an industrial conveyor system and, in particular, to a retarder apparatus which holds back a runaway conveyor and returns it to a normal speed.
In typical power and free conveyors, a load carrier is supported by load trolleys which are coupled to a lead or accumulating trolley that is driven when engaged by a pusher dog projecting from a continuously moving drive chain. The trolleys of the conveyor run in a free track independent from the drive chain which is supported by power trolleys in a parallel, power track. Instances occur in normal operation in which the load-carrying conveyor becomes disengaged from the pusher dog and creates a runaway condition. A free trolley retarder is employed in such systems to control the free conveyor when this occurs.
The conventional retarder is a shoe device that squeezes the sides of a passing free trolley to create a friction point in the system and impede movement of the conveyor unless it is powered by a pusher dog on the drive chain. The shoe is held in an interference position by springs that bear against the shoe and apply the frictional force.
It may be appreciated that since the conventional retarder is a friction device, it creates a "rub" or wear point where the shoe bears against the passing free trolley. Precise control of conveyor speed is difficult with the shoe-type retarder and wear on the free trolleys is inherent when using a retarder of this type.
It is, therefore, the primary object of the present invention to provide an improved retarder apparatus for controlling the speed of a free conveyor, which is capable of returning the conveyor to a predetermined, normal speed and wherein the retarding action is accomplished without significant wear on the trolley components.
In furtherance of the foregoing object, it is an important aim of this invention to provide such a retarder apparatus having a paddle member which extends into the path of travel of the conveyor and is engaged thereby and pushed as the conveyor passes.
Another important object of the invention is to provide such a retarder apparatus in which successive paddle members are connected with a brake means, not in contact with the conveyor, which limits the speed of movement of the conveyor in response to engagement of one of the paddle members by the conveyor.
Still another important object is to provide a retarder apparatus as aforesaid in which the paddle members are spaced along a flexible, endless, movable component trained around a pair of spaced, rotatable devices such as sprockets, a stretch of the component being disposed adjacent the path of travel of the conveyor for movement therewith when a paddle member is engaged, whereby the component is instantly driven at the speed of a passing conveyor and retarded by the brake means if appropriate.
Yet another object of this invention is to provide a retarder apparatus as aforesaid in which the brake means thereof comprises a centrifugal brake for accurately limiting the speed of the conveyor to a predetermined normal speed.
Furthermore, it is an important object to provide such an apparatus in which the stretch of the endless component and the paddle member thereon are supported against deflection or bending in response to engagement of the paddle member by the moving conveyor.
Further objects will become apparent as the detailed description proceeds.